Apparatus for producing extruded hollow board

ABSTRACT

Hollow synthetic board which may be used to replace corrugated paper board is continuously extruded of relatively soft thermoplastic resin, such as polyolefin, by apparatus having replaceable mandrels disposed in the cavity of an extrusion die. These mandrels are fastened in operative position by hollow screws which are part of the passage means for maintaining the interior of the synthetic board at ambient pressure. After leaving the die the extrusion alternately passes through a plurality of cooling and sizing sections. In the latter a vacuum is applied to the outer surface of the board to prevent collapse thereof prior to hardening of the extrusion. Temperature within the cooling sections is regulated so that the upstream sections are warmer than the downstream sections.

Meyers APPARATUS FOR PRODUCING EXTRUDED HOLLOW BOARD [75] Inventor:George E. Meyers, Dix Hills, N.Y.

[73] Assignee: Extrudyne, Inc., Amityville, N.Y.

[22] Filed: Jan. 24, 1972 [21] Appl. No.: 220,238

[52] U.S. Cl 425/326, 425/380, 425/467 [51] Int. Cl. B29c 1/00 [58]Field of Search... 425/325, 380, 461, 464, 467,

[56] References Cited UNITED STATES PATENTS 1,193,663 8/1916 Boyd et al425/325 1,310,509 7/1919 Specht 425/464 1,500,739 7/1924 Howard et al.425/464 X 2,616,126 11/1952 Merck et a1. 425/325 X 3,274,315 9/1966Kawamura 425/326 X 3,538,209 11/1970 Hegler 425/380 X Feb. 19, 1974Primary Examiner-Richard B. Lazarus Attorney, Agent,- or FirmOstrolenk,Faber, Gerb &

Soffen [5 7] ABSTRACT Hollow synthetic board which may be used toreplace corrugated paper board is continuously extruded of relativelysoft thermoplastic resin, such as polyolefin, by apparatus havingreplaceable mandrels disposed in the cavity of an extrusion die. Thesemandrels are fastened in operative position by hollow screws which arepart of the passage means for maintaining the interior of the syntheticboard at ambient pressure. After leaving the die the extrusionalternately passes through a plurality of cooling and sizing sections.In the latter a vacuum is applied to the outer surface of the board toprevent collapse thereof prior to hardening of the extrusion.Temperature within the cooling sections is regulated so that theupstream sections are warmer than the downstream sections.

10 Claims, 7 Drawing Figures PATENTEDFiB 19' m4 SHEET 1 0F 2 -N mmPATENTEDFEBIQ I974 SHEET 2 or 2 llNwll APPARATUS FOR PRODUCING EXTRUDEDHOLLOW BOARD This invention relates to extruding apparatus in generaland more particularly relates to an extruder for producing hollow boardfrom relatively soft polyolefin resin.

U. S. Pat. No. 3,274,315 issued Sept. 20, 1966, to Yuzo Kawamuraentitled Process for Unitized Construction of Synthetic Resin Board orCylinder describes apparatus for producing various embodiments of hollowsynthetic resin board that may be used as a substitute for papercorrugated board. In order to produce hollow synthetic resin boardhaving desirable strength and handling qualities, it is often desirableto utilize relatively soft thermoplastics such as polyolefins ratherthan a relatively hard plastic such as polyvinyl chloride. It appearsthat utilizing this relatively soft type of material presents certainproblems, making it impractical to produce hollow synthetic resin boardby utilizing equipment which the prior art had provided for producinghollow plastic forms.

Accordingly, a primary object of the instant invention is to providenovel extruding apparatus which is adapted to produce hollow board fromrelatively soft thermoplastics.

Another object is to provide extrusion apparatus of this type havingreplaceable mandrels in the die section.

Still another object is to provide apparatus of this type having a novelvacuum-cooling sizer means.

These objects as well as other objects of this invention will becomereadily apparent after reading the following description of theaccompanying drawings in which:

FIG. 1 is a schematic side elevation ofextruder apparatus constructed inaccordance with teachings of the instant invention.

FIG. 2 is a fragmentary perspective illustrating synthetic resin boardproduced by the apparatus of FIG. 1.

FIG. 3 is a fragmentary longitudinal cross-section through part of theextruder and sizer sections of the apparatus illustrated in FIG. 1.

FIG. 4 is a fragmentary front elevation looking in the direction ofarrows 4-4 of FIG. 3 of the die section.

FIG. 5 is a fragmentary cross-section taken through line 5-5 of FIG. 3.

FIG. 6 is an exploded perspective illustrating one of the replaceablemandrel elements and the elements for securing same in an operativeposition.

FIG. 7 is a fragmentary section taken through line 7-7 of FIG. 3. N I

Now referring to the figures. Extruding apparatus indicated generally byreference numeral 10 in FIG. 1 is intended to produce sheets ofsynthetic resin hollow board (FIG. 2) from pellets of a relatively softthermoplastic, such as polyolefin. Board 15 includes upper and lowerwalls 16, 17 maintained in spaced parallel relationship by closelyspaced continuous longitudinally extending ribs 18 constituting the sidewalls of continuous chambers 19 extending parallel to the direction ofmovement, indicated by arrow A, of board 15 through apparatus 10.Typically, board 15 has an overall thickness of 0.!25 inch, walls 16 and17 are each 0.035 inch thick, ribs 18 are each 0.035 inch thick, thecenter-to-center spacing between ribs 18 is 0.200 inch, and the overallwidth of sheet 15 is 39 inches. Sheet 15 may be cut to any lengthdesired from continuous extrusion 21.

Briefly, apparatus 10 includes hopper 11 which receives solidthermoplastic pellets that are directed into the barrel of a screw-typefeeder where heaters (not shown) transform the pelletized material intoa plastic state. Feeder 13 moves this plastic material from left toright with respect to FIG. 1, forcing it through compression head 14 anddie section 20 into sizer section 50. Even though die section 20 andsizer section 50 are illustrated as being in abutting relationship, inpractice these sections are usually closely spaced. The extrusion 21exiting from the right end of sizer section 50 passes between and isengaged by pairs of puller rolls 48, 49

which deliver extrusion 21 between anvil 47 and cutoff knife 46 operatedby solenoid 45. In a manner well known to the art, cutoff knife 46 andanvil 47 are mounted on a frame (not shown) which moves to the right atthe same speed as extrusion 21 during the period when knife 46 cutssheets 15 from extrusion 21. Sheets 15 are removed from the area ofknife 46 by belt-type conveyor 44 or other conveyor means (not Shown).

Die section 20 includes upper and lower die sections 23, 24, each havingan electric heater 25. Die sections 23, 24 are secured together inface-to-face relationship along line 99, to form low-profile die cavity26 therebetween. The cross-section of cavity 26 corresponds to theexternal shape of extrusion 21. Die section 23, 24 are provided withcutouts which receive complemen tary end extensions 31 of transversemandrel holder 30 to secure and operatively position the latter acrosscavity 26. The upstream end of holder 31 is provided with a conventionaltapered divider 32 that splits the plastic stream exiting fromcompression head 14 into portions that flow above and below holder 30.

Downstream face 33 of holder 30 is provided with a plurality of equallyspaced rectangular keying recesses 34 each of which receives theupstream end of an individual elongated mandrel 35. The latter is ofrectangular cross-section and tapers from end to end so that upstreamface 6 is of smaller area than downstream face 37. Circular recess 38formed in mandrel 35 adjacent face 37 houses head 39 of screw 40 thatextends through a longitudinal bore 41 in mandrel 3S and is received bythreaded aperture 42 in holder 31 to rigidly secure removable mandrel 35in operative position within die cavity 26 spaced from the wallsthereof. Transverse bore 43 extends through holder 30 and communicateswith all threaded apertures 42 thereof,

and also communicates with venting apertures 56 at opposite sides of diesection 20.

Sizer section 50 includes a plurality of vacuum forming sections 60spaced by a plurality of cooling sections 59. Each of the lattersections 59 is constructed with central passage 58 of a cross-sectioncorresponding to the external shape of board 15. Passage 58 issurrounded by a water jacket 57 having entrance port 54 and exit port 53for circulation of water within jacket 57.

Forming section 60 is provided with central passage 61 aligned with andof the same cross-section as passage 58. Manifold 62, connected to avacuum source through port 63, surrounds passage 61. The major opposedsurfaces 64, 65 are each provided with a plurality of extremely narrowtransverse slots 66 communicating with manifold 62, so that the reducedpressure within manifold 62 causes extrusion walls 16, 17 to be forcedagainst passage surfaces 64, 65 respectively, thereby preventingcollapse of walls l6, 17 during the period when these walls are in aplastic or semi-plastic state. It is noted that the pressure withincavities 19 is maintained at ambient, since chambers 19 between wallsl6, l7 communicate with ambient through the central passage 67 ofmandrel-fastening screw 40, holder passage 43, and die ports 56.

It is noted that warmer water is circulated in the more upstream coolingsections 59 that in the more downstream cooling sections 59. Inaddition, it is noted that the more upstream forming sections 60 areprovided with narrower slots 66 than are found in the more downstreamshaping section 60. Typically, the width of slots 66 is in the range offrom 0.005 inch to 0.030 inch.

Although there has been described a preferred embodiment of this novelinvention, many variations and modifications will now become apparent tothose skilled in the art. Therefore, this invention is to be limited notby the specific disclosure herein but only by the appending claims.

The embodiments of the invention in which an exclusive privilege orproperty is claimed are defined as follows.

1. Extrusion apparatus for producing synthetic resin board having upperand lower main walls connected together and maintained in spacedparallel relationship by a plurality of spaced longitudinally extendingcon tinuous ribs defining opposed side walls of longitudinally extendingchambers in said board; said extrusion apparatus including a die havinga longitudinally extending passage; feeding means for delivering resinto said die and forcing same downstream thereof through said passage; aholder secured to said die; a plurality of longitudinally extendingmandrels, one for each of said chambers, disposed within said passage,held by and projecting downstream from said holder; keying meansconfigured to enclosed a portion of each of said mandrels therebyoperatively positioning said mandrels with respect to each other and tosaid holder to prevent relative rotation therebetween; and securingmeans maintaining said mandrels individually removably mounted to saidholder in operative positions established by said keying means.

2. Extrusion apparatus as set forth in claim 1 in which the securingmeans comprises an individual screw for each of said mandrels extendingalong the axis thereof; each of said screws having a venting passageextending to the downstream end thereof so that said venting passagescommunicate with the internal chambers of the board.

3. Extrusion apparatus as set forth in claim 2 in which each of saidmandrels is tapered along its length so that a downstream cross-sectionthereof is larger than an upstream cross-section thereof.

4. Extrusion apparatus as set forth in claim 3 in which the die includesseparable sections and is provided with cutouts wherein complementaryportions at opposite ends of said holder are disposed to removablysecure the holder to said die via said cutouts.

5. Extrusion apparatus as set forth in claim 1 also including sizermeans positioned downstream of the die to receive an extrusion issuingtherefrom; said sizer means having a longitudinally extending passagethrough which the extrusion moves; said sizer means including aplurality of cooling sections and a plurality of shaping sections, witheach of said sections defining a portion of said passage; a first ofsaid shaping sections being interposed between a first and a second ofsaid cooling sections, and said second cooling section being interposedbetween said first shaping section and a second of said shapingsections; each of said first and second shaping sections including amanifold adapted to be maintained at a pressure below atmosphere; eachof said first and said second shaping sections including a pair ofopposed surfaces adjacent the upper and lower walls of the board; saidpair of opposed surfaces having aperture means communicating with saidmanifold whereby exterior portions of said upper and lower walls aresubjected to pressure below atmosphere to prevent collapse thereof assaid walls cool.

6. Extrusion apparatus as set forth in claim 5 in which said aperturemeans comprises slot means, said second shaping section being downstreamof the first shaping section and the slot means of the second shapingsection being wider than the slot means of the first shaping section.

7. Extrusion apparatus as set forth in claim 6 in which each of thefirst and second cooling sections includes passage means through whichcooling liquid is circulated, with the cooling liquid in the firstcooling section being warmer than the cooling liquid in the secondcooling section.

8. Extrusion apparatus as set forth in claim 7 in which the securingmeans comprises an individual screw for each of said mandrels extendingalong the axis thereof; each of said screws having a venting passageextending to the downstream end thereof, so that said venting passagescommunicate with the internal chambers of the board; each of saidmandrels being tapered along its length so that a downstreamcross-section thereof is larger than an upstream cross-section thereof.

9. Extrusion apparatus as set forth in claim 5 in which the securingmeans comprises an individual screw for each of said mandrels extendingalong the axis thereof; each of said screws having a venting passageextending to the downstream end thereof, so that said venting passagescommunicate with the internal chambers of the board.

l0. Extrusion apparatus as set forth in claim 9 in which each of saidmandrels is tapered along its length so that a downstream cross-sectionthereof is larger than an upstream cross-section thereof.

1. Extrusion apparatus for producing synthetic resin board having upperand lower main walls connected together and maintained in spacedparallel relationship by a plurality of spaced longitudinally extendingcontinuous ribs defining opposed side walls of longitudinally extendingchambers in said board; said extrusion apparatus including a die havinga longitudinally extending passage; feeding means for delivering resinto said die and forcing same downstream thereof through said passage; aholder secured to said die; a plurality of longitudinally extendingmandrels, one for each of said chambers, disposed within said passage,held by and projecting downstream from said holder; keying meansconfigured to enclosed a portion of each of said mandrels therebyoperatively positioning said mandrels with respect to each other and tosaid holder to prevent relative rotation therebetween; and securingmeans maintaining said mandrels individually removably mounted to saidholder in operative positions established by said keying means. 2.Extrusion apparatus as set forth in claim 1 in which the securing meanscomprises an individual screw for each of said mandrels extending alongthe axis thereof; each of said screws having a venting passage extendingto the downstream end thereof so that said venting passages communicatewith the internal chambers of the board.
 3. Extrusion apparatus as setforth in claim 2 in which each of said mandrels is tapered along itslength so that a downstream cross-section thereof is larger than anupstream cross-section thereof.
 4. Extrusion apparatus as set forth inclaim 3 in which the die includes separable sections and is providedwith cutouts wherein complementary portions at opposite ends of saidholder are disposed to removably secure the holder to said die via saidcutouts.
 5. Extrusion apparatus as set forth in claim 1 also includingsizer means positioned downstream of the die to receive an extrusionissuing therefrom; said sizer means having a longitudinally extendingpassage through which the extrusion moves; said sizer means including aplurality of cooling sections and a plurality of shaping sections, witheach of said sections defining a portion of said passage; a first ofsaid shaping sections being interposed between a first and a second ofsaid cooling sections, and said second cooling section being interposedbetween said first shaping section and a second of said shapingsections; each of said first and second shaping sections including amanifold adapted to be maintained at a pressure below atmosphere; eachof said first and said second shaping sections including a pair ofopposed surfaceS adjacent the upper and lower walls of the board; saidpair of opposed surfaces having aperture means communicating with saidmanifold whereby exterior portions of said upper and lower walls aresubjected to pressure below atmosphere to prevent collapse thereof assaid walls cool.
 6. Extrusion apparatus as set forth in claim 5 in whichsaid aperture means comprises slot means, said second shaping sectionbeing downstream of the first shaping section and the slot means of thesecond shaping section being wider than the slot means of the firstshaping section.
 7. Extrusion apparatus as set forth in claim 6 in whicheach of the first and second cooling sections includes passage meansthrough which cooling liquid is circulated, with the cooling liquid inthe first cooling section being warmer than the cooling liquid in thesecond cooling section.
 8. Extrusion apparatus as set forth in claim 7in which the securing means comprises an individual screw for each ofsaid mandrels extending along the axis thereof; each of said screwshaving a venting passage extending to the downstream end thereof, sothat said venting passages communicate with the internal chambers of theboard; each of said mandrels being tapered along its length so that adownstream cross-section thereof is larger than an upstreamcross-section thereof.
 9. Extrusion apparatus as set forth in claim 5 inwhich the securing means comprises an individual screw for each of saidmandrels extending along the axis thereof; each of said screws having aventing passage extending to the downstream end thereof, so that saidventing passages communicate with the internal chambers of the board.10. Extrusion apparatus as set forth in claim 9 in which each of saidmandrels is tapered along its length so that a downstream cross-sectionthereof is larger than an upstream cross-section thereof.